France, Belgium, Denmark, Poland,
the Czech Republic, and Slovakia have standardized on a socket
which is not compatible with the CEE 7/4 socket (Type F)
that is standard in Germany, the Netherlands, and other
continental European countries. The reason for incompatibility
is that earthing in the E socket is done by a round male pin
permanently mounted in the receptacle. Receptacles are installed
with the earth pin upwards and wired with left as live and right
as neutral. The plug itself is round with two round pins
measuring 4.8 × 19 mm, spaced 19 mm apart and a hole for the
socket's earth pin.
Type E receptacles will also accept Type C plugs. Type E plugs will also work in Type F receptacles. However, there is no earth connection in this case. Also, forcing the plug in may damage the receptacle.